[PATCH v4 3/3] serial: amba-pl011: add ACPI support to AMBA probe

[G Gregory]

On 4 January 2016 at 23:13, Timur Tabi <timur at codeaurora.org> wrote:
> On Wed, Dec 23, 2015 at 8:19 AM, Aleksey Makarov
> <aleksey.makarov at linaro.org> wrote:
>> From: Graeme Gregory <graeme.gregory at linaro.org>
>>
>> In ACPI this device is only defined in SBSA mode so
>> if we are coming from ACPI use this mode.
>>
>> Signed-off-by: Graeme Gregory <graeme.gregory at linaro.org>
>> Signed-off-by: Aleksey Makarov <aleksey.makarov at linaro.org>
>> ---
>>  drivers/tty/serial/amba-pl011.c | 37 ++++++++++++++++++++++++++-----------
>>  1 file changed, 26 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
>> index 899a771..974cb9e 100644
>> --- a/drivers/tty/serial/amba-pl011.c
>> +++ b/drivers/tty/serial/amba-pl011.c
>> @@ -2368,18 +2368,33 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
>>         if (!uap)
>>                 return -ENOMEM;
>>
>> -       uap->clk = devm_clk_get(&dev->dev, NULL);
>> -       if (IS_ERR(uap->clk))
>> -               return PTR_ERR(uap->clk);
>> -
>> -       uap->vendor = vendor;
>> -       uap->lcrh_rx = vendor->lcrh_rx;
>> -       uap->lcrh_tx = vendor->lcrh_tx;
>> -       uap->fifosize = vendor->get_fifosize(dev);
>> -       uap->port.irq = dev->irq[0];
>> -       uap->port.ops = &amba_pl011_pops;
>> +       /* ACPI only defines SBSA variant */
>> +       if (has_acpi_companion(&dev->dev)) {
>> +               /*
>> +                * According to ARM ARMH0011 is currently the only mapping
>> +                * of pl011 in ACPI and it's mapped to SBSA UART mode
>> +                */
>> +               uap->vendor     = &vendor_sbsa;
>> +               uap->fifosize   = 32;
>> +               uap->port.ops   = &sbsa_uart_pops;
>> +               uap->fixed_baud = 115200;
>
> I'm confused by this patch.  We already have code like this in
> tty-next, in the form of sbsa_uart_probe():
>
> https://kernel.googlesource.com/pub/scm/linux/kernel/git/gregkh/tty/+/tty-next/drivers/tty/serial/amba-pl011.c#2553
>
Because Russell expressed unhappiness at that code existing. So this
is an alternative method to do same thing with ACPI.

If the "arm,sbsa-uart" id was added to drivers/of/platform.c as an
AMBA id then the same could be done for DT as well.

Ultimately this patch is optional depending on maintainers opinion!

Graeme